Biochemical and physiological studies of spermatozoa from inbred strains of mice will be continued, emphasizing differences between spermatozoa from mice carrying segregation distorting t-alleles and ones without such alleles. The general biochemical genetics of spermatozoa are also being studied in an attempt to see if any genes are expressed post-meiotically. F1 and backcrosses will be made to study the control of spermatozoal beta-glucuronidase. Continued characterizations of spermatozoal RNA by pulse-labelling will be continued while we wish to attempt to study its synthesis in density-gradient separated, testicular cells. Further studies of testicular isoenzymes will be performed to continue the elucidation of the genetic control of spermatogenesis.